There are many situations where it is desired to create a light field that has a specified luminance profile. Light projection systems have a very wide range of applications from architectural lighting to the display of lifelike images. The projected light patterns can be dynamic (e.g. video), static (used for static images or static applications like the beams of typical car headlights projected through a lens onto the road, made by arbitrarily shaped optical surfaces, etc.). Light may be projected onto a wide range of screens and other surfaces which may be flat or curved. Such surfaces may be fully reflective (like a canvas used in a cinema, a wall or a building) or partially reflective (such as the windshield of a vehicle). Screens may be low-gain or high-gain, Lambertian or highly directional, high-contrast or lower in contrast. Light may be projected onto solid objects or onto a medium in a volume (such as fog).
Markets for and applications of light projectors include digital cinema, in-door and out-door advertising, medical imaging (both for display of images, as well as capture by a smart light source), large venue and live events or performances, automotive heads up displays, car head-lights and rear-lights, automotive entertainment and information displays, home-theatre, portable business projection, television and displays for consumer applications, military applications, aviation applications (like cockpit displays, smart landing-assistance, individual passenger entertainment displays), structured light sources for industrial applications, automotive headlights and other applications.
Various devices may be used to spatially modulate light. These may be called spatial light modulators (SLMs). Most SLMs provide a 2D array of independently and individually addressable pixels. Some examples of SLMs are reflective SLMs such as digital micro-mirror devices (DMDs), liquid crystal on silicon (LCoS) devices and transmissive SLMs such as LCD panels, transmissive LCD chips such as high-temperature polysilicon (HTPS) or low-temperature polysilicon (LTPS); and partially reflective/partially transmissive SLMs such as micro-electro-mechanical systems (MEMS) based systems in which some of incident light is transmitted and some of incident light is reflected. One problem is that most readily available spatial light modulation technologies are subtractive. These SLM technologies operate by absorbing or removing undesired light. This contributes to the more general problem that light projection and often general illumination technologies tend to have undesirably high energy consumption and may also have an undesirably limited peak luminance.
Additional considerations apply to light projectors that are applied to project images. For example, in such projectors raised black-levels, undesirably low contrast and limited colour-saturation can be concerns.
These limitations can mean that a dark viewing environment such as a cinema, a dark living room, or some other lighting-controlled environment, is needed to get the best out of projected imagery. This limits the possible applications for projectors.
In all fields of technology including light projection achieving a desired level of performance at a competitive cost can be an issue.
There is a general need for light projection systems that ameliorate one or more of the above-noted problems.